KR102295451B1 - Glass substrate for display and manufacturing method thereof - Google Patents

Abstract

Provided are a glass substrate that satisfies a high strain point while suppressing the devitrification temperature to a low level, and a method for manufacturing the same.
Glass substrate for display. SiO ₂ , Al ₂ O ₃ is contained, in terms of mass %, B ₂ O ₃ is 0% or more and less than 3%, BaO is 5-14%, Sb ₂ O ₃ is substantially free, devitrification It consists of glass whose temperature is 1235 degrees C or less and the strain point is 720 degrees C or more. Alternatively, SiO ₂ , Al ₂ O ₃ is contained, and in terms of mass%, B ₂ O ₃ is 0% or more and less than 3%, MgO is 1.8% or more, BaO is 5-14%, Sb ₂ O ₃ is substantially free, (SiO ₂ +MgO+CaO)-(Al ₂ O ₃ +SrO+BaO) is less than 42%, the devitrification temperature is 1260° C. or less, and the strain point consists of a glass of 720° C. or more. . The manufacturing method of the glass substrate for a display. A melting step of dissolving a glass raw material prepared in a predetermined composition using at least direct current heating, a forming step of molding the molten glass melted in the melting step into flat glass, a step of slowly cooling the flat glass, and a slow cooling step of controlling the cooling conditions of the flat glass so as to reduce the thermal contraction rate of the type glass.

Description

Glass substrate for display and manufacturing method thereof

This invention relates to the glass substrate for displays and its manufacturing method. In particular, the present invention relates to a glass substrate for a low-temperature polysilicon thin film transistor (hereinafter, referred to as LTPS-TFT (Low-Temperature-Polycrystalline-Silicon Thin-Film-Transistor)) display. Moreover, this invention relates to the glass substrate for oxide semiconductor thin film transistors (henceforth OS-TFT(Oxide-Semiconductor Thin-Film-Transistor)) display. More specifically, this invention relates to the glass substrate for displays whose said display is a liquid crystal display. Or it is related with the glass substrate for displays whose said display is an organic electroluminescent display. Moreover, it is related with the glass substrate for flat panel displays whose said display is a flat panel display.

Cross-referencing of related applications

This application claims the priority of Japanese Patent Application No. 2015-131780 of an application on June 30, 2015, and all of those descriptions are specifically used as an indication here.

For displays mounted on portable devices, etc., it is desired to apply LTPS to the manufacture of thin film transistors (TFTs) for reasons such as being able to reduce power consumption. Heat treatment at high temperature is required. On the other hand, in recent years, the display of a small portable device is calculated|required more and more high definition. Therefore, the thermal contraction of the glass substrate which causes the pitch shift of a pixel and arises at the time of display panel manufacture poses a problem. Moreover, also in the glass substrate in which OS-TFT is formed, suppression of thermal contraction becomes a subject similarly.

Generally, the thermal contraction rate of a glass substrate can be reduced by making high the strain point (strain point) of glass, making a glass transition point (henceforth Tg) high, or slowing down the slow cooling rate. From such a background, in order to reduce thermal contraction rate, the technique of making the strain point of glass high is disclosed (patent document 1). Moreover, the technique which adjusts the ratio of the gradient of an average density curve in the temperature range from an annealing point to strain point vicinity, and an average coefficient of linear expansion is disclosed (patent document 2). Moreover, in order to reduce thermal contraction rate, the technique of making Tg high is disclosed (patent document 3). Moreover, in recent years, since high resolution of a display panel is increasingly requested|required, in the technique of patent document 3, it has become reduction of insufficient thermal contraction rate. For this reason, the technique which makes the strain point of glass 725 degreeC or more is also disclosed (patent document 4).

Patent Document 1: Japanese Patent Laid-Open No. 2010-6649

Patent Document 2: Japanese Patent Laid-Open No. 2004-315354

Patent Document 3: Japanese Patent Laid-Open No. 2011-126728

Patent Document 4: Japanese Patent Laid-Open No. 2012-106919

All descriptions of Patent Documents 1 to 4 are specifically incorporated herein by reference.

In recent years, since high-definition is calculated|required more and more, making thermal contraction rate further smaller is calculated|required. When increasing the strain point of the glass substrate in order to further reduce the heat shrinkage ratio, it is necessary to increase the content of SiO ₂ or Al ₂ O ₃ in the glass, and as a result, tends to increase in the resistivity of the molten glass. In recent years, in order to melt|dissolve glass efficiently in a dissolution tank, direct electric heating may be used. When direct current heating is used and the specific resistance of a molten glass rises, an electric current will flow to the refractory material which comprises the melting tank rather than a molten glass, As a result, it turned out that there exists a possibility that the problem that a melting tank will melt|dissolve may arise. However, in invention described in the said patent document 1, it is not considered at all about the specific resistance of a molten glass. Therefore, when it is going to manufacture the glass of patent document 1 through melting|fusing by direct electric heating, there is strong concern that the problem of the said melting tank dissolution loss will arise. Moreover, the said problem becomes more remarkable from the point which is calculated|required in recent years to make the strain point of glass higher and to make high resolution increasingly calculated|required.

In addition, since the strain point of the glass disclosed in Patent Document 2 is 682 to 699° C., in order to make the gradient of the average density curve sufficiently small for heat shrinkage, it is necessary to make the slow cooling rate very slow, and there is a problem that productivity decreases. there was. Moreover, since loss-of-clarity temperature was 1287 degreeC or more of the glass disclosed by patent document 2, there also existed a problem that loss-of-clarity was easy to generate|occur|produce. Moreover, the above-mentioned problem becomes especially remarkable when shaping|molding using the down-draw method.

Moreover, in manufacture of the display using a glass substrate, it is calculated|required to improve productivity, for example, the improvement of the productivity of the process of thinning the glass substrate with a thin film transistor is also calculated|required. The productivity of the process of thinning a glass substrate largely depends on the time taken for the etching of a glass substrate. Therefore, it is calculated|required by a display glass substrate that the improvement of productivity by a raise of an etching rate, and reduction of thermal contraction rate are compatible. However, about the glass substrate of the said patent document 4, although a strain point was high, there existed a problem that an etching rate was not considered.

Then, this invention aims at providing the glass substrate which satisfy|fills a high strain point, suppressing loss-of-clarity temperature low, and its manufacturing method. In particular, an object of the present invention is to provide a display glass substrate suitable for a display using LTPS-TFT or OS-TFT, and a method for manufacturing the same.

The present invention is as follows.

[One]

SiO ₂ , Al ₂ O ₃ containing,

In terms of mass %,

B ₂ O ₃ is 0% or more and less than 3%,

BaO is 5 to 14%,

substantially free of Sb ₂ O _{3 ,}

The loss-of-clarity temperature is 1235 degrees C or less, and

The glass substrate for a display which consists of glass whose strain point is 720 degreeC or more.

[2]

SiO ₂ , Al ₂ O ₃ containing,

In terms of mass %,

B ₂ O ₃ is 0% or more and less than 3%,

MgO is 1.8% or more,

BaO is 5 to 14%,

substantially free of Sb ₂ O _{3 ,}

(SiO ₂ +MgO+CaO)-(Al ₂ O ₃ +SrO+BaO) is less than 42%,

The loss-of-clarity temperature is 1260 degrees C or less, and also

The glass substrate for a display which consists of glass whose strain point is 720 degreeC or more.

[3]

The glass substrate according to [1] or [2], wherein the glass substrate is maintained at a temperature of 500° C. for 30 minutes, and then the thermal contraction rate represented by the following formula in the case of allowing to cool to room temperature is 15 ppm or less.

Heat shrinkage rate (ppm) = {Shrinkage amount of glass before and after heat treatment / length of glass before heat treatment} × 10 ⁶

[4]

The glass substrate according to any one of [1] to [3], wherein the glass substrate has an etching rate greater than 75 µm/h.

[5]

The glass substrate according to any one of [1] to [4], wherein the thin film transistor formed using low-temperature polysilicon or oxide semiconductor is a glass substrate for a flat panel display formed on the surface of the glass substrate.

[6]

A melting step of dissolving glass raw materials prepared in a predetermined composition using at least direct current heating;

A forming step of forming the molten glass melted in the melting step into flat glass;

The glass according to any one of [1] to [5], which is a step of slowly cooling the flat glass, and includes a slow cooling step of controlling cooling conditions of the flat glass to reduce the thermal contraction rate of the flat glass. The manufacturing method of the glass substrate for displays which manufactures a board|substrate.

According to the glass substrate of this invention mentioned above, it becomes possible to manufacture the glass substrate which satisfies a high strain point, suppressing loss-of-clarity temperature low. Thereby, the glass substrate for displays which can reduce the thermal contraction at the time of display manufacture, especially the glass substrate for displays suitable for the flat panel display using LTPS-TFT or OS-TFT can be provided with high productivity.

In the specification of the present application, unless otherwise specified, the content of the glass is expressed in mass%, and the content expressed in % means mass%. The ratio of the components constituting the glass composition is expressed by mass ratio.

The glass substrate for displays (1st aspect) of this invention,

SiO ₂ , Al ₂ O ₃ containing,

In terms of mass %,

B ₂ O ₃ is 0% or more and less than 3%,

BaO is 5 to 14%,

substantially free of Sb ₂ O _{3 ,}

The loss-of-clarity temperature is 1235 degrees C or less, and

It consists of glass with a strain point of 720 degreeC or more.

The glass substrate for a display (2nd aspect) of this invention,

SiO ₂ , Al ₂ O ₃ containing,

In terms of mass %,

B ₂ O ₃ is 0% or more and less than 3%,

MgO is 1.8% or more,

BaO is 5 to 14%,

substantially free of Sb ₂ O _{3 ,}

(SiO ₂ +MgO+CaO)-(Al ₂ O ₃ +SrO+BaO) is less than 42%,

The loss-of-clarity temperature is 1260 degrees C or less, and also

It consists of glass whose strain point is 720 degreeC or more.

Hereinafter, embodiment of the glass substrate for displays of this embodiment is demonstrated. In addition, unless otherwise indicated, the following description is common to the 1st aspect and 2nd aspect of this invention.

Glass constituting the glass substrate for a display of the present invention, it contains SiO ₂ and Al ₂ O _3.

SiO ₂ is a component of the skeleton of glass, and thus is an essential component. When the content decreases, the strain point decreases and the coefficient of thermal expansion tends to increase. Also, if the SiO ₂ content is too small, it is difficult to screen low-density glass substrate. On the other hand, it tends to be a SiO ₂ content is too high, increase the specific resistance of the molten glass, and the dissolution is difficult increased to the melting temperature markedly. Further, the SiO ₂ content is too large, the slow etching rate. In this regard, the content of SiO ₂ is, it may be properly adjusted. SiO ₂ content of the glass is preferably, for example, a range of 45-80%. The content of SiO ₂ is more preferably 50-75%, or 50 to 70%, more preferably 52-68%, more preferably in the range of 55-65%.

Al ₂ O ₃ is an essential component to increase the strain point. If the Al ₂ O ₃ content is too small, it decreases transformation point. Further, if the Al ₂ O ₃ content is too small, there is a tendency that the etching rate is also lowered by the Young's modulus and an acid. On the other hand, Al ₂ O ₃ content is too large, so that the devitrification temperature of the glass increases, the reduction in thread covered with, there is a tendency that moldability is worse. From this point of view, it can be appropriately adjusted. The content of Al ₂ O ₃ of the glass, for example in the range of 10-35%. The content of Al ₂ O ₃ is preferably 13-30%, more preferably 15-25%, more preferably 15-23%, more preferably in the range of 16-22%.

B ₂ O ₃ is, by lowering the high temperature viscosity of the glass and is a component for improving the melting property. That is, since the viscosity in the vicinity of the melting temperature is reduced, solubility is improved. Moreover, it is also a component which reduces loss-of-clarity temperature. B ₂ O ₃ content is small, tends to decrease the solubility and covered within the chamber. B ₂ O ₃ content is too large, the strain point and the Young's modulus is reduced. Further, by volatilization of B ₂ O ₃ of glass forming, devitrification is likely to occur. In particular, since the glass with a high strain point tends to have a high molding temperature, the said volatilization is accelerated|stimulated and generation|occurrence|production of devitrification becomes a remarkable problem. Further, by volatilization of B ₂ O ₃ of glass melting, the glass becomes uneven remarkably, striae tends to occur. From such a viewpoint, B ₂ O ₃ content is 0% or more and less than 3%. B ₂ O ₃ content is preferably 0 to 2.8%, more preferably 0 to 2.6%, still more preferably 0.1 to 2.4%, still more preferably 0.3 to 2.2%, still more preferably 0.5 It is in the range of -2.0%.

MgO is a component which improves solubility, and in the 2nd aspect of this invention, it is an essential component. Moreover, since it is a component difficult to increase a density in alkaline-earth metal, when the content is relatively increased, it will become easy to achieve low density. By containing it, the specific resistance and melting temperature of a molten glass can be reduced. However, when there is too much content of MgO, since the devitrification temperature of glass will rise rapidly, it will become easy to devitrify especially in a shaping|molding process. From this viewpoint, in the second aspect of the present invention, the MgO content is in the range of 1.8 to 15%, preferably 1.8 to 13%, more preferably 1.9 to 10%, still more preferably 1.9 to 7%. . Alternatively, in the first aspect of the present invention, the MgO content is preferably 0 to 15%, more preferably 0 to 13%, still more preferably 0 to 10%.

Although CaO is not essential, when it contains it, it is a component effective in improving the solubility of glass, without raising the loss-of-clarity temperature of glass rapidly. Moreover, since it is a component difficult to increase a density in alkaline-earth metal oxide, when the content is relatively increased, it will become easy to achieve low density. When there is too little content, there exists a tendency which the raise of the specific resistance of a molten glass, and a devitrification resistance fall generate|occur|produce. When there is too much CaO content, there exists a tendency for a thermal expansion coefficient to increase and a density to rise. From such a viewpoint, CaO content becomes like this. Preferably it is 0 to 20 %, More preferably, it is 0 to 15 %, More preferably, it is the range of 0 to 10 %.

SrO is a component which can lower|hang the loss-of-clarity temperature of glass. Although SrO is not essential, when it is made to contain, devitrification resistance and solubility will improve. However, when there is too much SrO content, a density will rise. From such a viewpoint, the SrO content is 0 to 15%, preferably 0 to 10%, more preferably 0 to 7%, still more preferably 0 to 5%, still more preferably 0 to 3%. is the range

BaO is an essential component which can lower|hang effectively the loss-of-clarity temperature of glass, and the specific resistance of a molten glass. When BaO is contained, devitrification resistance and solubility will improve. However, when there is too much content of BaO, a density will rise. Moreover, from a viewpoint of an environmental load and the point which a thermal expansion coefficient tends to increase, BaO content is the range of 5 to 14 %. BaO content becomes like this. Preferably it is 6 to 13.5 %, More preferably, it is 7 to 13 %, More preferably, it is 8 to 12 %, More preferably, it is the range of 8.5 to 12 %.

MgO, CaO, SrO, and BaO are components which reduce the specific resistance and melting temperature of a molten glass, and improve solubility. When there are too few MgO+CaO+SrO+BaO (henceforth RO) which is the total amount of content of MgO, CaO, SrO, and BaO, solubility will deteriorate. When there is too much RO, a strain point and a Young's modulus will fall, and a density and a coefficient of thermal expansion will rise. From this point of view, RO is preferably in the range of 5 to 35%, more preferably in the range of 9 to 30%, still more preferably in the range of 10 to 27%, still more preferably in the range of 12 to 25%.

Li ₂ O and Na ₂ O are components that may increase the thermal expansion coefficient of glass and damage the substrate at the time of heat treatment. Moreover, it is also a component which reduces a strain point. On the other hand, since the specific resistance of a molten glass can be reduced, it can suppress that a melting tank erodes by containing it. The content of Li ₂ O In the above aspect is that the 0~0.5%, and, more preferably does not contain substantially. The content of Na ₂ O, is that the 0~0.5%, more preferably from 0~0.2%. Further, Na ₂ O is, in view of the difficult to lower the transformation point compared to the components Li ₂ O, preferably in the Na ₂ O> Li ₂ O. Further, in the viewpoint of preventing the glass substrate is eluted from the deterioration of the TFT characteristics, Li ₂ O and Na ₂ O is preferred that, not containing substantially.

K ₂ O is a component which raises the basicity of glass and accelerates|stimulates clarification. Moreover, it is a component which reduces the specific resistance of a molten glass. When it contains, since the specific resistance of a molten glass will fall, it can prevent that an electric current flows to the refractory body which comprises a melting tank, and it can suppress that a melting tank erodes. Moreover, since it can suppress that a dissolution tank erodes when the refractory body which comprises a dissolution tank contains zirconia and zirconia elutes from a dissolution tank to a molten glass, the devitrification resulting from a zirconia can also be suppressed. Moreover, since the glass viscosity in melt|dissolution temperature vicinity is reduced, solubility and clarification property improve. On the other hand, the K ₂ O content is too large, there is a tendency of increasing the thermal expansion coefficient and lowering the transformation point. From such a viewpoint, the K ₂ O content is preferably 0 to 0.8%, more preferably 0.01 to 0.6%, still more preferably 0.1 to 0.5%.

Li ₂ O, Na ₂ O, and K ₂ O are components which raise the basicity of glass, make oxidation of a clarifier easy, and exhibit clarification property. Moreover, it is a component which reduces the viscosity in melting temperature and improves solubility. Moreover, it is also a component which reduces the specific resistance of a molten glass. When Li ₂ O, Na ₂ O, and K ₂ O are contained, the specific resistance of a molten glass will fall, and clarification and solubility will improve. In particular, it can prevent that an electric current flows excessively to the refractory body which comprises a melting tank, and it can suppress that a melting tank is eroded. Moreover, since the elution of the zirconia to glass from a dissolution tank can be suppressed when a dissolution tank contains zirconia, the devitrification resulting from a zirconia can also be suppressed. Moreover, since the viscosity of molten glass is reduced, solubility and clarification property improve. However, too large amount of sum of the content of Li ₂ O, Na ₂ O and K ₂ O, there is a danger of the elution from the glass substrate deteriorating the TFT characteristics. Moreover, a strain point falls and there exists a tendency for a thermal expansion coefficient to increase. The total amount of the contents of Li ₂ O, Na ₂ O and K _{2 O (hereinafter referred to as R 2} O) is preferably 1.0% or less, more preferably 0.01 to 1.0%, still more preferably 0.01 to 0.8 %, more preferably 0.1 to 0.5%.

ZrO ₂ and TiO ₂ are components that improve the strain point of glass. However, since the amount of ZrO ₂ and TiO ₂ amount to too much ground, the devitrification temperature is markedly elevated, and tends to be lowered within the chamber is full. In particular, since ZrO ₂ has a high melting point and is hardly soluble, it causes a problem that a part of the raw material is deposited at the bottom of the dissolution tank. When these undissolved components are mixed into the glass substrate, it causes deterioration of the quality of the glass as inclusions. Further, TiO ₂ is, since the component to color the glass, it is not desirable for the substrate for a display. From such a viewpoint, in the glass substrate of this embodiment _{, 0 to 10 % is preferable, respectively, as for content of ZrO 2} and TiO ₂ , More preferably, it is 0 to 5 % of range, It is still more preferable not to contain substantially. do.

ZnO is a component that improves solubility. However, it is not an essential ingredient. When ZnO content increases too much, there exists a tendency for loss-of-clarity temperature to rise, a strain point to fall, and to a density rise. From such a viewpoint, ZnO content becomes like this. Preferably it is 0 to 5 %, More preferably, it is the range of 0 to 2 %, It is still more preferable not to contain substantially.

The glass substrate of this embodiment can contain a clarifier. Although it will not restrict|limit as a clarifier in particular as long as the load on environment is small and the clarification property of glass is excellent, For example, at least 1 sort(s) selected from the group of metal oxides of Sn, Fe, Ce, Tb, Mo, and W is mentioned. can A glass substrate of the present embodiment does not include Sb ₂ O ₃ substantially. As the Sb ₂ O ₃ is not substantially free of, it is possible to reduce the burden on the environment. As a refining agent, the SnO ₂ are suitable. When there is too little content of a clarifier, bubble quality will deteriorate, and when it increases too much, it may become a cause, such as devitrification and coloring. Content of a clarifier changes with the kind of clarifier, and the composition of glass. For example, SnO _2, and the total amount of Fe ₂ O ₃ is, that the 0.05~0.50%, and preferably, more preferably 0.05~0.40%.

SnO ₂ is a second fining obtained by the refining effect in more than _{1600 ℃, Li 2 O, Na} 2 O and K ₂ O to a trace amount, for a flat panel display glass substrate (for example, for which can not be contained outside, Li ₂ O, Na the ₂ O and K ₂ O is the sum amount of the few refining agent which can be used in the manufacture of 0.01~0.8%). However, SnO ₂ is not desirable that at the same time from the viewpoint of the easy-component to generate devitrification themselves, inhibit, because devitrification component to promote the generation of the devitrification of the other components, is added in a large amount.

In addition, since the glass with a high strain point (for example, glass with a strain point of 720 degreeC or more) tends to become high easily compared with glass with a low strain point (for example, glass with a strain point less than 720 degreeC), devitrification In order to suppress , the temperature of the molten glass in a shaping|molding process may have to be made high compared with glass with a low strain point. Here, it is preferable that the molded object used by the overflow down-draw method is comprised including the refractory material containing zirconia from a viewpoint of creep resistance and heat resistance. When using overflow downdraw as a shaping|molding method, it is necessary to raise the temperature of a molded object, so that it is going to make the temperature of the molten glass in a shaping|molding process high. However, when the temperature of a molded object becomes high, zirconia will elute from a molded object, and there exists a problem that devitrification of the said zirconia becomes easy to generate|occur|produce. In particular, the glass containing a large amount of SnO _2, there is devitrification, devitrification of the zirconia is easily prone to occur due to the SnO ₂ SnO ₂ due to the zirconia.

Moreover, the glass with a high strain point (for example, glass with a strain point of 720 degreeC or more) tends to also become high easily at the temperature which melt|dissolves glass-making feedstock compared with glass with a low strain point (for example, glass with a strain point less than 720 degreeC). There is this. Here, it is preferable that the dissolution tank which performs a dissolution process is comprised including the high zirconia-type refractory material containing zirconia from a viewpoint of erosion resistance. Further, from the viewpoint of energy efficiency, it is preferable to melt the glass raw material by electric melting or a combination of electric melting and other heating means. However, a high strain point, as described in this embodiment, and if the melting of glass can not contain Li ₂ O, Na ₂ O and K ₂ O only in trace amounts, since the specific resistance of the molten glass size, and zirconia An electric current flows in a system refractory body, and it becomes easy to generate|occur|produce the problem that zirconia will elute in a molten glass. If I zirconia is eluted, the easy-to devitrification and devitrification of SnO ₂ in the above-described zirconia occurrence tendency.

That is, from the viewpoint of suppressing the devitrification of zirconia and SnO _2, in the glass substrate of the present embodiment, SnO ₂ is not desirable to content exceeding about 0.8%. In view of this, it SnO ₂ content is, for example, to be 0.01 or less or more preferably 0.8%, and is preferably 0.02~0.6%, more preferably 0.05~0.50%, and more preferably in the range of 0.05~0.40%.

Fe ₂ O ₃ is, in addition to having an action as a refining agent, a component for lowering the specific resistance of the molten glass. High-temperature viscosity is high and in poorly soluble glass, in order to reduce the specific resistance of a molten glass, it is preferable to make it contain. However, when the Fe ₂ O ₃ content is too large, the glass is colored, the transmittance is reduced. Therefore, Fe ₂ O ₃ content is within a range of 0~0.1%, preferably 0~0.08%, more preferably 0.001~0.06%, more preferably 0.001 to 0.05%, more preferably from 0.001 to 0.04 % range.

In the present embodiment refining agent, it is preferred to use a combination of SnO ₂ and Fe ₂ O _3. From the viewpoint of suppressing devitrification, it is not preferable to contain a lot of SnO ₂ as described above. However, in order to fully acquire a clarification effect, it is calculated|required to contain a clarifier more than predetermined value. Thus, by a combination of SnO ₂ and Fe ₂ O _3, without increasing the content of SnO ₂ so cause devitrification, it is obtained a sufficient refining effect can, to manufacture the air bubbles are small glass substrate. The total amount of SnO ₂ and Fe ₂ O ₃ is preferably in the range of 0.05 to 0.50%, more preferably in the range of 0.05 to 0.45%, still more preferably in the range of 0.05 to 0.40%.

When the mass ratio of the content of _{SnO 2} to the total amount of _{SnO 2} and Fe ₂ O _{3 (SnO 2} /(SnO ₂ +Fe ₂ O ₃ )) is too large, devitrification tends to occur, and when too small, sufficient clarification effect is obtained. It becomes impossible, and the glass may be colored. Therefore, Preferably it is the range of 0.6-1.0, More preferably, it is the range of 0.7-0.98.

A glass substrate of this embodiment, it is preferred from the problem of environmental load, As ₂ O ₃ is substantially free. A glass substrate of the present embodiment, from the problem of environmental load, Sb ₂ O ₃ is not substantially free of.

It is preferable that the glass substrate of this embodiment does not contain PbO and F substantially from an environmental reason.

In addition, in this specification, "substantially not containing" means that the material used as a raw material of these components is not used in the said glass raw material, The component contained as an impurity in the glass raw material of another component, a dissolution tank , it does not exclude mixing of components eluted into glass from the manufacturing apparatus, such as a molded object.

The content of SiO ₂ and the difference between the content of _{Al 2 O 3 1/4 SiO 2 -} (1/4 × Al 2 O 3) , the value is too large, there is a fear that the etching rate decreases. From this point of view, SiO ₂ -(1/4×Al ₂ O ₃ ) is 65 or less. On the other hand, when the value of SiO ₂ -(1/4×Al ₂ O ₃ ) is too small, devitrification resistance may decrease. From such a viewpoint, SiO ₂ -(1/4×Al ₂ O ₃ ) is preferably 40% to 65%, more preferably 45% to 60%, still more preferably 50% to 55%.

_{(SiO 2} +MgO+CaO)-(Al ₂ O ₃ +SrO+BaO), which is the difference between the total amount of SiO ₂ , MgO and CaO, and Al ₂ O ₃ , SrO, and BaO, is an index of the etching rate, and the value is too high When large, an etching rate will fall. On the other hand, when a value is too small, devitrification resistance will fall. From this point of view, (SiO ₂ +MgO+CaO)-(Al ₂ O ₃ +SrO+BaO) is preferably less than 42%, more preferably 41% or less, still more preferably 25 to 41%, More preferably, it is 30 to 40% of the range.

The weight ratio _{(SiO 2 + Al 2 O 3} ) / (B 2 O 3 + RO) , the strain point is mainly as indicators in devitrification resistance. When a value is too small, a strain point will fall. On the other hand, when a value is too large, solubility and devitrification resistance will fall. Therefore, the mass ratio (SiO ₂ +Al ₂ O ₃ )/(B ₂ O ₃ +RO) is preferably 1 to 8, more preferably 2 to 7, still more preferably 2.5 to 6.5, still more preferably is in the range of 3 to 6.

B ₂ O ₃ +RO+ZnO mainly serves as an index of solubility. When a value is too small, solubility will fall. On the other hand, when a value is too large, a strain point will fall and a thermal expansion coefficient will increase. From such a viewpoint, B ₂ O ₃ +RO+ZnO is preferably in the range of 5 to 35%, more preferably 9 to 30%, still more preferably 12 to 28%, still more preferably 15 to 25%. % range.

The content of SiO ₂ and the total amount of the content of _{Al 2 O 3 SiO 2 + Al} 2 O 3 is, if too low, tends to be lowered strain point tends to be too large, deterioration in yarn covered. Therefore, SiO ₂ + Al ₂ O ₃ is 70-90% is desirable, preferably 73-88%, more preferably 75-85%, and more preferably in the range of 77-83%.

Mass ratio of _{B 2 O 3 / (SiO 2} + Al 2 O 3) is, and is mainly an index of solubility, within the chamber teeming, the transformation point. _{B 2 O 3 / (SiO 2} + Al 2 O 3) is too large, the strain point is lowered. On the other hand, if too small, the _{B 2 O 3 / (SiO 2} + Al 2 O 3), there is a tendency that solubility and deterioration within the chamber is full. _{B 2 O 3 / (SiO 2} + Al 2 O 3) is preferably from 0 to 0.050, more preferably from 0 to 0.045, more preferably 0.001 to 0.040, and more preferably in the range of 0.005 to 0.035.

The weight ratio SiO ₂ / Al ₂ O _3, the value is too large, there is a possibility that the etching rate decreases, if the value is too small, there is concern within the chamber is full to be lowered. In this regard, the weight ratio SiO ₂ / Al ₂ O ₃ is 1.5 to 4.5 2.0 to 4.0 is the preferred, more preferably, more preferably in the range of 2.5 to 3.7. In a glass having a composition that is the value of SiO ₂ + Al ₂ O ₃ approximately, the etching rate is remarkably more dependent on the SiO ₂ / Al ₂ O _3. A high strain point, within the chamber teeming, the viewpoint of both the etching rate, SiO ₂ + Al ₂ O ₃ is 70-90%, and also preferably in the SiO ₂ / Al ₂ O ₃ 1.5~4.5, more preferably is, SiO ₂ + Al ₂ O ₃ is 73-88%, and also preferably has a SiO ₂ / Al ₂ O ₃ in the range of 2.0 to 4.0.

B ₂ O ₃ and RO are both components which improve solubility. B ₂ O _3, but has a good effect for solidifying within the chamber teeming, is lowered strain point is too large. On the other hand, although RO has the effect of reducing the specific resistance of glass, when there is too much, devitrification resistance will fall. From the viewpoint of both the solubility and teeming within chamber, the mass ratio B ₂ O ₃ / RO is to be in the range of 0 to 0.5 0.01 to 0.3 are preferred, and more preferably from 0 to 0.4, more preferably, to more preferably is in the range of 0.02 to 0.2.

Even if mass ratio BaO/RO has too small a value or too large, loss-of-clarity temperature rises. Moreover, when the value of BaO/RO becomes large, a Young's modulus becomes low, and also a density rises further, and a specific resistance also rises. Therefore, the mass ratio BaO/RO becomes like this. Preferably it is 0-0.9, Preferably it is 0.1-0.85, More preferably, it is the range of 0.2-0.8.

Even if mass ratio (3*BaO)/(MgO+CaO+SrO) has too small a value or too large, loss-of-clarity temperature rises. On the other hand, when the value of (3xBaO)/(MgO+CaO+SrO) becomes large, the Young's modulus becomes low, furthermore, the density increases, and the specific resistance also increases. Therefore, mass ratio (3xBaO)/(MgO+CaO+SrO) becomes like this. Preferably it is 5.0 or less, Preferably it is 0.5-5, More preferably, it is the range of 1-5.

The mass ratio CaO/RO is preferably 0 to 0.8, more preferably 0.1 to 0.7, still more preferably 0.15 to 0.6, still more preferably 0.2 to, in order to effectively lower the devitrification temperature without increasing the density too much. It is in the range of 0.5.

As for the mass ratio (MgO/(RO+ZnO)), when a value is small, the loss-of-clarity temperature will become low, and there exists a tendency for a Young's modulus to become low. Further, the density increases and the specific resistance also increases. On the other hand, when a value is large, loss-of-clarity temperature will rise and Young's modulus will become low. Therefore, mass ratio (MgO/(RO+ZnO)) becomes like this. Preferably it is 0.01-0.8, Preferably it is the range of 0.02-0.6, 0.03-0.4.

As for mass ratio SrO/CaO, when a value is small, loss-of-clarity temperature will become low, and there exists a tendency for a Young's modulus to become low. Further, the density increases and the specific resistance also increases. On the other hand, when a value is large, loss-of-clarity temperature will rise and Young's modulus will become low. Therefore, mass ratio (MgO/(CaO+SrO)) is 0.6 or less, Preferably it is 0.36 or more, Preferably it is 0.4 or more.

The weight ratio _{(SiO 2 + Al 2 O 3} ) / (B 2 O 3 + RO + (10 × R 2 O)) is, and is an indicator of mainly the transformation point and solubility. When a value is too small, a strain point will fall. Therefore, the weight ratio _{(SiO 2 + Al 2 O 3} ) / a _{(B 2 O 3 + RO +} (10 × R 2 O)) is 1.0 or more, preferably in the range of 2.0 or more. On the other hand, when a value is too large, solubility and devitrification resistance will fall. Therefore, the weight ratio _{(SiO 2 + Al 2 O 3} ) / (B 2 O 3 + RO + (10 × R 2 O)) is preferably from 1.0 to 10, more preferably in the range of 2.0 to 7. (SiO ₂ +Al ₂ O ₃ )/(B ₂ O ₃ +RO+(10×R ₂ O)) is preferably 2.5 to 5.

RE ₂ O ₃ is the total amount of rare earth metal oxides, and as rare earth metal oxides, Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , Pr ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ are exemplified. . RE ₂ O ₃ is a component that increases a density and a coefficient of thermal expansion. In addition, the cost is also a high component. Therefore, RE ₂ O ₃ is 0 or more and less than 1.0% (inclusive of 0), More preferably, it is the range of 0-0.5% (inclusive of 0), It is especially preferable not to contain substantially.

From the viewpoint of sikindago prevent an increase in the density and thermal expansion coefficient, and further reduce the cost, Y ₂ O ₃ and La ₂ O is preferable, that is substantially free of.

In the 2nd aspect of this invention, loss-of-clarity temperature of a glass substrate is 1260 degrees C or less. Preferably it is 1250 degrees C or less, More preferably, it is 1240 degrees C or less, More preferably, it is 1230 degrees C or less, More preferably, it is 1220 degrees C or less. On the other hand, in the 1st aspect of this invention, the loss-of-clarity temperature of a glass substrate is 1235 degreeC or less, Preferably it is 1230 degrees C or less, More preferably, it is 1225 degrees C or less, More preferably, it is 1220 degrees C or less, More preferably, it is 1210 degrees C or less. am. It becomes easy to shape|mold a glass plate by the overflow down-draw method, so that loss-of-clarity temperature is low. By applying the overflow down-draw method, since the process of grinding|polishing a glass substrate surface can be omitted, the surface quality of a glass substrate can be improved. Moreover, production cost can also be reduced. When the loss-of-clarity temperature is too high, since loss-of-clarity is easy to generate|occur|produce, there exists a tendency for application to the overflow down-draw method to become difficult.

A glass substrate of this embodiment, and an average thermal expansion coefficient (100-300 ℃) in ^{100 ℃ ~300 ℃ 50.0 × 10 -7} ℃ -1 or less, from 28.0 to 50.0 preferably from × 10 ^-7 ℃ ^-1 and more preferably 33.0 to 47.0×10 ^-7 °C ^-1 , still more preferably 33.0 to 46.0×10 ^-7 °C ^-1 , still more preferably 35.0 to 44.0×10 ^-7 °C ^-1 , still more preferably It is preferably in the range of 38.0 to 43.0×10 ^-7 ℃ ^-1. When the coefficient of thermal expansion is large, there is a tendency for thermal shock and thermal contraction rate to increase in the heat treatment step. Moreover, when a thermal expansion coefficient is large, it will become difficult to reduce thermal contraction rate. Moreover, even if a thermal expansion coefficient is large or small, it becomes difficult to take matching of thermal expansion coefficient with peripheral materials, such as a metal and a thin film formed on a glass substrate, and there exists a possibility that a peripheral member may peel.

Generally, when a glass substrate has a low strain point, it will become easy to generate|occur|produce thermal contraction in the heat processing process at the time of display manufacture. The strain point of the glass substrate of this embodiment is 720 degreeC or more, Preferably it is 725 degreeC or more, More preferably, it is 730 degreeC or more, More preferably, it is 735 degreeC or more.

As for the glass substrate of this embodiment, it is preferable that thermal contraction rate is 15 ppm or less. When the thermal contraction rate becomes too large, a large pitch shift of a pixel will be caused, and it will become impossible to implement|achieve a high-definition display. In order to control thermal contraction rate in a predetermined range, it is preferable to make the strain point of a glass substrate into 720 degreeC or more or 730 degreeC or more. In addition, when the rate of heat shrinkage is set to 0 ppm, it is required to lengthen the slow cooling process very long, or to perform a heat shrinkage reduction treatment (offline slow cooling) after the slow cooling and cutting steps, but in this case, the productivity decreases and the cost increases. In consideration of productivity and cost, the thermal contraction rate is, for example, preferably 0.1 ppm to 15 ppm, or 0.5 ppm to 15 ppm, more preferably 1 ppm to 15 ppm, still more preferably 1 ppm to 13 ppm, still more preferably 2 ppm -10 ppm.

In addition, thermal contraction rate is shown by the following formula after hold|maintaining a glass substrate at the temperature of 500 degreeC for 30 minute(s), and the heat processing left to cool to normal temperature after that is performed.

Heat shrinkage rate (ppm) = {Shrinkage amount of glass before and after heat treatment / length of glass before heat treatment} × 10 ⁶

At this time, "the amount of shrinkage of the glass before and after heat treatment" is "the length of the glass before heat treatment - the length of the glass after heat treatment".

The density of the glass substrate of this embodiment is from a viewpoint of weight reduction of a glass substrate and weight reduction of a display, Preferably it is 3.0 g/cm<3> or less, More preferably, it is 2.8 g/cm<3> or less, More preferably, it is 2.65 g/cm<3> or less. is below. When a density becomes high too much, weight reduction of a glass substrate will become difficult and it will become difficult to aim at weight reduction of a display as well.

When the transition point (hereinafter, referred to as Tg) of the glass becomes low, heat shrinkage tends to occur easily in the heat treatment step of display manufacturing. Tg of the glass substrate of this embodiment becomes like this. Preferably it is 770 degreeC or more, More preferably, it is 775 degreeC or more, More preferably, it is 780 degreeC or more. In order to make the Tg of the glass substrate in the above range, in the range of the composition of the glass substrate of the present embodiment, for example, SiO ₂ and a lot of components such as Al ₂ O _3, or B ₂ O _3, RO, R It is appropriate to decrease the component of _{2 O.}

The glass of this embodiment ^{preferably has a temperature at which the viscosity is 10 2.5} [dPa·s] (hereinafter referred to as melting temperature), preferably 1680° C. or less, more preferably in the range of 1500 to 1680° C., still more preferably Preferably it is 1520-1660 degreeC, More preferably, it is the range of 1540-1640 degreeC. Glass with a low melting temperature tends to have a low strain point. In order to make the strain point high, it is necessary to also make the melting temperature high to some extent. However, when melting temperature is high, the load to a dissolution tank will become large. In addition, since a large amount of energy is used, the cost also increases. Moreover, when applying electrolysis to glass melting, an electric current may flow not glass but the heat-resistant brick which forms a melting tank, and a melting tank may be damaged. To the melting temperature of the glass in the above-described range, in the range of the composition of the glass substrate of the present embodiment, to lower the viscosity, for example B ₂ O _3, suitable to contain in the range of the above-described components, such as RO do.

As for the molten glass at the time of manufacturing the glass substrate of this embodiment, a specific resistance (in 1550 degreeC) becomes like this. Preferably it is 30-700 ohm-cm, More preferably, it is 30-400 ohm-cm, More preferably, it is 30-300 ohm. -cm, More preferably, it is the range of 50-300 ohm-cm. When specific resistance becomes too small, the electric current value required for melting may become excessive, and restrictions on facilities may arise. Also, there is a tendency that the consumption of the electrode increases. When the specific resistance of a molten glass becomes large too much, an electric current may flow not glass but the heat-resistant brick which forms a melting tank, and a melting tank may be damaged. The specific resistance of the molten glass is, mainly, can be adjusted to the above range by controlling the content of _{RO, R 2 O, Fe 2} O 3.

It is preferable that the glass which comprises the glass substrate of this embodiment has an etching rate of 50 micrometers/h or more. The higher the etching rate, the higher the productivity. In particular, when a glass substrate is etched and weight reduction is achieved after the TFT side and the glass substrate on the color filter side are matched, the etching rate influences productivity. However, when an etching rate becomes high too much, although productivity at the time of display manufacture will improve, the devitrification resistance of glass will fall. Moreover, the rate of thermal contraction also increases easily. The etching rate is preferably 60 to 140 µm/h, more preferably 70 to 120 µm/h, still more preferably greater than 75 and 120 µm/h or less, still more preferably 77 to 120 µm/h. In order to increase the etching rate of the glass, the value of SiO ₂ +MgO+CaO-(Al ₂ O ₃ +SrO+BaO), SiO ₂ -(1/4×Al ₂ O ₃ ), or SiO ₂ /Al ₂ O ₃ make it smaller In this embodiment, the said etching rate is defined as what was measured under the following conditions. The etching rate (μm/h) in the present specification refers to a unit time ( It is the amount of thickness decrease (μm) of one surface of the glass substrate per hour).

As for the glass substrate of this embodiment, plate|board thickness may be 0.1-1.1 mm, or the range of 0.3-1.1 mm may be sufficient. However, it is not intended to limit to this range. The plate thickness may be, for example, in the range of 0.3 to 0.7 mm and 0.3 to 0.5 mm. When the thickness of a glass plate is too thin, the intensity|strength of glass substrate itself will fall. For example, it becomes easy to generate|occur|produce the breakage at the time of flat panel display manufacture. When the plate thickness is too thick, it is undesirable for a display requiring thinning. Moreover, since the weight of a glass substrate becomes heavy, it becomes difficult to achieve weight reduction of a flat panel display. Moreover, when performing the etching process of a glass substrate after TFT formation, the etching process amount increases, and cost and time are required.

The glass substrate of this embodiment is used for manufacture of the flat panel display which etch-processes the glass substrate surface after array color filter alignment, for example. The glass substrate of this embodiment is suitable for the glass substrate for a display (however, a CRT (braun tube) display is excluded). In particular, the glass substrate of this embodiment is suitable for the glass substrate for flat panel displays in which LTPS-TFT or OS-TFT is formed. Specifically, it is suitable for the glass substrate for liquid crystal displays, and the glass substrate for organic electroluminescent displays. In particular, it is suitable for the glass substrate for LTPS-TFT liquid crystal displays, and the glass substrate for LTPS-TFT organic electroluminescent displays. Especially, it is suitable for the glass substrate for displays, such as a portable terminal which high definition is calculated|required.

<Flat Panel Display>

This embodiment includes the flat panel display which formed LTPS-TFT or OS-TFT in the glass substrate surface, As for this flat panel display, a glass substrate is the glass substrate of the said this embodiment. The flat panel display of the present embodiment may be, for example, a liquid crystal display or an organic EL display.

<The manufacturing method of a glass substrate>

The manufacturing method of the glass substrate for displays of this embodiment uses the melting process which melt|dissolves the glass-making feedstock which combined by the predetermined composition at least using direct current heating, for example, and the molten glass which melt|dissolved in the said melting process flat plate type It has the shaping|molding process of shape|molding with glass, and the slow cooling process of slowly cooling the said flat glass.

In particular, it is preferable that the said slow cooling process is a process of controlling the cooling conditions of the said flat glass so that the thermal contraction rate of the said flat glass may be reduced.

[Dissolution process]

In a melting process, the glass-making feedstock prepared so that it might have a predetermined composition is melt|dissolved using, for example, direct energization heating and/or combustion heating. Glass-making feedstock can be suitably selected from well-known materials. It is preferable to melt|dissolve glass-making feedstock using direct electricity heating at least in a melting|fusing process from a viewpoint of energy efficiency. Moreover, it is preferable that the dissolution tank which performs a dissolution process is comprised including the high zirconia type refractory material. The said predetermined composition can be suitably adjusted in the range which satisfy|fills the content mentioned above about each component of glass, for example.

[Forming process]

At a shaping|molding process, the molten glass melt|dissolved in the melting process is shape|molded into flat glass. As for the shaping|molding method to flat glass, the down-draw method, especially the overflow down-draw method is suitable, for example, A glass ribbon is shape|molded as flat glass. In addition, the float method, the redraw method, the roll-out method, etc. can be applied. By employing the down-draw method, compared with the case of using other molding methods such as the float method, since the main surface of the obtained glass substrate is formed as a free surface that is not in contact with anything other than the atmosphere, it has extremely high smoothness, and the glass substrate after molding Since the grinding|polishing process of the surface becomes unnecessary, manufacturing cost can be reduced and productivity can also be improved. Moreover, since both main surfaces of the glass substrate shape|molded using the down-draw method have a uniform composition, when etching process is performed, it can etch uniformly irrespective of the front and back at the time of shaping|molding.

[Slow cooling process]

By appropriately adjusting the conditions at the time of slow cooling, the thermal contraction rate of a glass substrate is controllable. In particular, it is preferable to control the cooling conditions of the flat glass to reduce the thermal contraction rate of the flat glass. As mentioned above, the thermal contraction rate of a glass substrate is 15 ppm or less, Preferably it is 13 ppm or less, More preferably, it is 1-13 ppm. In order to manufacture a glass substrate having such a numerical rate of thermal contraction, for example, when using the down-draw method, the cooling rate of the glass ribbon as flat glass is set within the temperature range from Tg to (Tg-100° C.) , it is preferable to perform slow cooling so that it may be set to 30-300 degreeC/min. When the cooling rate is too fast, the rate of thermal contraction cannot be sufficiently reduced. On the other hand, when a cooling rate is too slow, while productivity will fall, the problem that a glass manufacturing apparatus (slow cooling furnace) will enlarge will arise. The preferable range of a cooling rate is 30-300 degreeC/min, 50-200 degreeC/min is more preferable, 60-120 degreeC/min is still more preferable. The glass substrate of this embodiment can be manufactured more reliably by making a cooling rate into 30-300 degreeC/min. In addition, after cutting the flat glass at the downstream of the slow cooling process, the thermal contraction rate can also be reduced by performing slow cooling separately offline. becomes necessary Therefore, as mentioned above, it is preferable also from a viewpoint of productivity and cost to control so that a thermal contraction rate can be reduced in a slow cooling process so that offline slow cooling can be abbreviate|omitted. In addition, in this specification, the cooling rate of a glass ribbon shall show the cooling rate of the width direction center part of a glass ribbon.

Example

Hereinafter, this embodiment is demonstrated in more detail based on an Example. However, this embodiment is not limited to an Example. In the Examples and Comparative Examples shown below, the physical properties described below were measured.

(transformation point)

Measurement was performed using a beam bending measuring apparatus (manufactured by Tokyo Kogyo Co., Ltd.), and the strain point was calculated according to the beam bending method (ASTM C-598).

(devitrification temperature)

The glass was crushed, passed through a 2380 µm sieve, and the glass particles remaining on the 1000 µm sieve were placed in a platinum boat. This platinum boat was hold|maintained for 5 hours in the electric furnace which has a temperature gradient of 1050-1380 degreeC, after that, it was taken out from the furnace, and the devitrification which generate|occur|produced inside the glass was observed with the optical microscope of 50 times. The highest temperature at which loss-of-clarity was observed was made into loss-of-clarity temperature.

(Method for measuring average coefficient of thermal expansion α and Tg in the range of 100 to 300°C)

Differential thermal dilatometer (Thermo Plus2) TMA8310) was used. The temperature increase rate at this time was 5 degree-C/min. Based on the measurement result, the average coefficient of thermal expansion and Tg in the temperature range of 100-300 degreeC were calculated|required.

(heat shrinkage)

The thermal contraction rate was calculated|required by the scribe wire method with respect to the glass of the magnitude|size of 90 mm - 200 mm x 15-30 mm x 0.3-1 mm. As the heat treatment for heat shrinkage measurement, using an air circulating furnace (N120/85HA manufactured by Nabertherm), the temperature was maintained at 500° C. for 30 minutes and allowed to cool to room temperature.

Heat shrinkage rate (ppm) = {Shrinkage amount of glass in heat treatment/Distance between scribe lines of glass before heat treatment} × 10 ⁶

In addition, when the glass raw material is melted in a platinum crucible and then flowed out onto an iron plate and the heat shrinkage of the glass obtained by cooling and solidifying is measured, cutting and grinding are performed so as to have a thickness of 0.5 mm, and using an electric furnace, Tg+ After hold|maintaining at the temperature of 15 degreeC for 30 minutes, the glass taken out to the outside of the furnace at the rate of 150-250 degreeC/min of temperature-fall rate was used.

(density)

The density of the glass was measured by the Archimedes method.

(etch rate)

The etching rate (µm/h) is when the glass (12.5 mm × 20 mm × 0.7 mm) is immersed in an etchant (200 mL) at 40°C adjusted to have an HF concentration of 1 mol/kg and an HCl concentration of 5 mol/kg for 1 hour. It calculated|required by measuring the thickness reduction amount (micrometer), and calculating the thickness reduction amount (micrometer) of one surface of a glass substrate per unit time (1 hour).

Hereinafter, the composition and evaluation of an Example are demonstrated.

The glasses of Examples 1-63 were produced according to the following procedure so that it might become the glass composition shown in Table 1. About the obtained glass, the strain point, loss-of-clarity temperature, Tg, the average coefficient of thermal expansion (alpha) in the range of 100-300 degreeC, thermal contraction rate, a density, and an etching rate were calculated|required.

[Table 1-1]

[Table 1-2]

[Table 1-3]

[Table 1-4]

[Table 1-5]

[Table 1-6]

[Table 1-7]

[Table 1-8]

[Table 1-9]

[Table 1-10]

[Table 1-11]

The raw materials of each component were combined and melt|dissolution, clarification, and shaping|molding were performed so that it might become the glass composition shown in Table 1.

The loss-of-clarity temperature of Examples 1-63 among the glass obtained as mentioned above was 1260 degreeC or less, and the strain point was 720 degreeC or more (Example of the glass substrate of Claim 2). Among them, in Examples 1 to 6, 9, 15 to 18, 21, 25, 29 to 31, 34 to 45, 47 to 57, and 59 to 60, the devitrification temperature is 1235°C or less, and the strain point is 720°C or more. It was (Example of the glass substrate of Claim 1). Moreover, even when glass-making feedstock was melt|dissolved using direct electric heating and the glass substrate was manufactured by the overflow down-draw method, the same result was obtained. Therefore, by using these glasses, the glass substrate which can be used for the display to which LTPS-TFT is applied by the overflow down-draw method can be manufactured. Moreover, these glass substrates are suitable also as a glass substrate for OS-TFT.

Claims (10)

SiO ₂ , Al ₂ O ₃ containing,
In terms of mass %,
B ₂ O ₃ is 0% or more and less than 3%,
BaO is 5 to 14%,
The sum of Li ₂ O, Na ₂ O and K ₂ O is 0.2% or more,
substantially free of Sb ₂ O _{3 ,}
SrO/CaO is 0.35 or more,
The loss-of-clarity temperature is 1235 degrees C or less, and
The glass substrate for a display which consists of glass whose strain point is 720 degreeC or more. SiO ₂ , Al ₂ O ₃ containing,
In terms of mass %,
B ₂ O ₃ is 0% or more and less than 3%,
MgO is 1.8% or more,
BaO is 5 to 14%,
The sum of Li ₂ O, Na ₂ O and K ₂ O is 0.2% or more,
substantially free of Sb ₂ O _{3 ,}
(SiO ₂ +MgO+CaO)-(Al ₂ O ₃ +SrO+BaO) is less than 42%,
SrO/CaO is 0.35 or more,
The loss-of-clarity temperature is 1260 degrees C or less, and
The glass substrate for a display which consists of glass whose strain point is 720 degreeC or more. 3. The method of claim 1 or 2,
The said glass substrate is hold|maintained at the temperature of 500 degreeC for 30 minutes, and the thermal contraction rate represented by the following formula at the time of leaving to cool to room temperature after that is 15 ppm or less, The glass substrate for displays.
Heat shrinkage rate (ppm) = {Shrinkage amount of glass before and after heat treatment / length of glass before heat treatment} × 10 ⁶ 3. The method of claim 1 or 2,
The said glass substrate is a glass substrate for displays whose etching rate is larger than 75 micrometers/h. 3. The method of claim 1 or 2,
A glass substrate for a display, wherein a thin film transistor formed using low-temperature polysilicon or an oxide semiconductor is a glass substrate for a flat panel display formed on a surface of a glass substrate. A melting step of dissolving glass raw materials prepared in a predetermined composition using at least direct current heating;
A forming step of forming the molten glass melted in the melting step into flat glass;
It is a step of slowly cooling the flat glass, and manufacturing the glass substrate according to claim 1 or 2, comprising a slow cooling step of controlling the cooling conditions of the flat glass to reduce the thermal contraction rate of the flat glass , a method for manufacturing a glass substrate for a display. 3. The method of claim 1 or 2,
Li ₂ O, 1.0% or less, a glass substrate for a display the amount of the sum of Na ₂ O and K ₂ O. 3. The method of claim 1 or 2,
Li ₂ O is from 0 to 0.5%, a glass substrate for a display. 3. The method of claim 1 or 2,
Na ₂ O is from 0 to 0.5%, a glass substrate for a display. delete